Apparatus and method for improving air quality in street canyons

ABSTRACT

A double skin façade (DSF) for a building is disclosed. The DSF has a first façade, a second façade, and a gap extending therebetween. Movement of air is driven in an upward direction toward an upper end of the DSF, causing movement of air contaminants from a lower end of the DSF to the upper end of the DSF, and thereby enhancing the air quality of the street canyon by removing air contaminants from a street level adjacent the building. Also disclosed is a building having a DSF, and a method of enhancing air quality in a street canyon by constructing a DSF on a building.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application claims priority under 35 U.S.C. § 119(e) to U.S.Ser. No. 62/814,643, filed Mar. 6, 2019, the entirety of which is herebyexpressly incorporated by reference herein.

BACKGROUND

Urban Design resides at the interface of Planning, Engineering, andArchitecture. The design of cities to support growing populations is adance where planners balance zoning, policy, and legal frameworks,engineers lay infrastructure, and architects orchestrate buildings withfaçades that activate streetscapes where people live and work. Urbanhuman health stands to benefit from the intersection of urbanclimatology and urban design. Planners are working to great effect tocreate a “sense of place,” reduce traffic, and increase walkability.Architects develop great buildings to enhance the streetscape and“activate” communities along the streets; however, in many cases, urbanclimatology is taken into account only as an extreme weather event,increased wind loads, or to identify a need for building energyefficiencies. The existing inventory of buildings and streets are slowlybeing redesigned to accommodate more foot traffic, and new towns arebeing designed to counter sprawl and increase health outcomes bypromoting walkability. City air quality issues caused by the buildingsand street morphology—urban street canyons—are little understood andfrequently overlooked during planning and design. It has becomenecessary to identify strategies to mitigate urban criteria airpollutants within these same urban street canyons. One method is tointegrate buildings not only as effective contributors to urbanstreetscape but also as infrastructure to mitigate air pollutants.

In trying to make streets more walkable to boost economies and helppeople live healthier lifestyles, it is important to take into accountthat street plantings are insufficient to mitigate air pollution in avariety of urban configurations. Planners, engineers, and architectsmust become familiar with the ramifications of street configurations andurban form as they relate to the potential of trapped criteria airpollutants. Architects can effectively create design interventionswithin their building façades that can mitigate criteria air pollutantsthat are found in these urban street canyon configurations.

Urbanization and Air Quality Issues

As urbanization and densification increases, the microclimates ofurban/higher density suburban areas change. Oke explains in BoundaryLayer Climates (Metheun & Co. Ltd., London, 2^(nd) edition, 1987) thatthe largest source of air pollution in North America is the atmosphericboundary layer of a city caused by its morphology with pollutantsproduced primarily by automobiles. The pollution mix is dominated by CO,CO₂, NO₂, Hc, and small particulates. When sufficient sunlight isavailable, this leads to the development of photochemical smog andsecondary pollutants such as volatile organic compounds (VOCs).

The removal of air pollutants at the street level is dependent upon airtemperature stratification. Free flow of the air is important todiffusing the pollution into a larger volume. Dispersion is best whenthere is strong instability and deep mixing characteristics during sunnysummer time conditions. The worst conditions for dispersion tend tooccur where there is a temperature inversion and the boundary layer isstable. This suppresses turbulence, effectively eliminating upwardmotion.

In areas characterized by low buildings, the exchange betweenstreet-level where car pollutants are emitted and above roof-leveldepends upon the ratio of the height of the buildings to the width ofthe street/sidewalk between the adjacent buildings. If the streets arenarrow, air exchange is restricted (panel (a) of FIG. 1) as compared tothat in a more open arrangement, where the vortex circulation aidsstreet-level flushing (panel (b) of FIG. 1).

Problem Identification

Current guidelines for buildings in urban cores and the establishment ofnew town centers many times provide requirements for height to widthratios that shape the relationship between the building and street. Thiscan result in an urban morphology that creates a form called an urbanstreet canyon. According to a Wikipedia entry, a “street canyon” (alsoknown as an urban canyon) is a place where the street is flanked bybuildings on both sides, creating a canyon-like environment. Classicexamples of these human-built canyons are made when streets separatedense blocks of structures, especially skyscrapers. Urban canyons affectvarious local conditions, including temperature, wind, air quality, andradio reception. Typically, a street canyon is a relatively narrowstreet with tall, continuous buildings on both sides of the road. Butnow the term “street canyon” is used more broadly, and the geometricaldetails of the street canyon are used to categorize them.

The most important geometrical detail about a street canyon is the ratioof the canyon height (H) to canyon width (W), H:W, which is referred toas the aspect ratio. The value of the aspect ratio can be used toclassify street canyons as follows: (1) Regular canyon: aspect ratio ˜1and no major openings on the canyon walls, (2) Avenue canyon: aspectratio <0.5, and (3) Deep canyon: aspect ratio ˜2.

In urban design, the movement of vehicular traffic, pedestrians, andbikers governs the width ratio based upon activity within theright-of-way (ROW) between buildings. When it is considered that mostNew Towns are 4-6 stories (approximately 62′-74′) and the predominantwidth of the ROW (approximately 64′-72′), the morphology of the urbancanyon creates the <1:1 height to width ratio where meteorologicalinfluences including wind speed and direction create boundary layerinversions beneath the urban canopy layer. At these ratios, airpollution can become sequestered within the urban boundary layer. Theproblem becomes one where unhealthy places are unintentionally created.“Green Infrastructure” is assumed to offset some of the air pollution,but in actuality, street plantings, integrated building plantings, andsurface mounted living walls serve only as surfaces for deposition ofparticulates and minor conversion of CO₂; they do not actually mitigateVOCs.

Design Guides for Urban Cores and Town Centers

While Form Based Codes are used to restore buildings in urban cores andestablish new town centers, their height to width ratios shape therelationship between the building and street with their resultinggeometry creating a form called an urban street canyon. The movement oftraffic, pedestrians, and bikers governs the width ratio based uponactivity within the right-of-way between buildings. In association withthe CNU, the National Association of City Transportation Officials(NACTO) has created a compendium of principles and practices forComplete Streets based on the local Transect, which includes the designcapacity for safe interaction of automobiles, pedestrians, bikers,multi-modal transit, and urban infrastructure.

Air pollution is being addressed world-wide. High density, highpopulation cities are searching for guidelines and study methodologiesto address growth and development and their interactions with urbanclimatology. The approach to study the interaction of wind, air quality,and buildings, employs two basic methodologies. In general, numericalanalysis through the use of computational fluid dynamics (CFD) and windtunnel tests are commonly used for individual building and urban windengineering studies. The advantage of using CFD is that it is cheaperthan wind tunnel tests for less demanding tasks. Validation andverification of CFD results are still necessary research issues whichcan be accomplished with wind tunnel studies. CFD is, however, a usefultool to give a first order quantitative graphical representation.

BRIEF DESCRIPTION OF THE DRAWINGS

The patent or application file contains at least one drawing executed incolor. Copies of this patent or patent application publication withcolor drawing(s) will be provided by the Office upon request and paymentof the necessary fee.

FIG. 1 is a schematic showing that in a street canyon with a narrowstreet between buildings (such as, but not limited to, a <1:1 height towidth aspect ratio), air exchange is restricted (a), while in a streetcanyon with a more open arrangement (>1:1.5), the vortex circulationaids street-level flushing (b).

FIG. 2 contains photographs showing wind tunnel results which illustratethe four conditions of the relationship between a street canyon and theperpendicular airflow therein.

FIG. 3 is a photograph showing one aspect of the urban canyon model inthe wind tunnel and laser beam used to trace the particulate movementwithin the model.

FIG. 4 is a photograph showing another aspect of the urban canyon modelin the wind tunnel and laser beam used to trace the particulate movementwithin the model.

FIG. 5 is a photograph showing another aspect of the urban canyon modelin the wind tunnel and laser beam used to trace the particulate movementwithin the model.

FIG. 6 is a photograph showing the laser beam used to trace theparticulate movement in the wind tunnel experiment.

FIG. 7 is a photograph showing another aspect of the urban canyon modelin the wind tunnel and laser beam used to trace the particulate movementwithin the model.

FIG. 8 shows wind tunnel results for the model urban canyon using hotsmoke.

FIG. 9 shows wind tunnel results for the model urban canyon using dryice vapor.

FIG. 10 shows further wind tunnel results for the model urban canyonusing dry ice vapor.

FIG. 11 shows wind tunnel results for the model urban canyon using coldsmoke.

FIG. 12 shows further wind tunnel results for the model urban canyonusing cold smoke.

FIG. 13 shows further wind tunnel results for the model urban canyonusing cold smoke.

FIG. 14 shows further wind tunnel results for the model urban canyonusing dry ice vapor.

FIG. 15 shows further wind tunnel results for the model urban canyonusing dry ice vapor.

FIG. 16 shows further wind tunnel results for the model urban canyonusing hot smoke.

DETAILED DESCRIPTION

One method of mitigating urban criteria air pollutants and addressingurban health concerns while working within the guidelines established toaddress increasing urbanization is to utilize buildings as effectivecontributors to urban streetscape and green infrastructure. Buildingsare interconnected with urban infrastructure, thereby serving as aresource and not just a load. For example, regenerative building façadescan interact with the streetscape component. The present disclosuredescribes the use of a double skin façade (DSF) on a building toremediate environmental pollutants beyond the building perimeter.

In at least one non-limiting embodiment, the present disclosure isdirected to a building having a capability of enhancing quality of theair adjacent the building, wherein the building has a double skin façade(DSF), wherein the DSF has (1) a first façade and a second façade facingand substantially parallel to the first façade, (2) an upper end and alower end, and (3) a gap between the first façade and the second façadeextending from the lower end to the upper end. In certain particular(but non-limiting) embodiments, the DSF further includes at least onemechanical ventilator (such as, but not limited to, a fan) positionedadjacent or near the upper end of the DSF (with the term “near”generally being defined in this instance as being within, for example,about 0 feet to about 20 feet); when the at least one mechanicalventilator is in an operating mode, it drives movement of air in anupward direction toward the upper end of the DSF causing movement of aircontaminants from the lower end of the DSF to the upper end of the DSF,thereby enhancing the air quality adjacent the building by removal ofthe air contaminants from a street level adjacent the building. Thestreet canyon having the building may have an aspect ratio of at leastabout 1.0, or at least about 1.5, for example.

In at least one non-limiting embodiment, the present disclosure isdirected to a method of enhancing air quality in a street canyonincluding the steps of (a) constructing a double skin façade (DSF) on abuilding, wherein the DSF is any of the DSF's described or otherwisecontemplated herein; and (b) causing the at least one mechanicalventilator of the DSF to be in an operational mode, whereby movement ofair is driven in an upward direction toward the upper end of the DSF,causing movement of air contaminants from the lower end of the DSF tothe upper end of the DSF, thereby enhancing the air quality of thestreet canyon by removing air contaminants from a street level adjacentthe building. The street canyon having the building may have an aspectratio of at least about 1.0, or at least about 1.5, for example.

In certain particular (but non-limiting) embodiments, the DSF used inthe method has (1) a first façade and a second façade facing andsubstantially parallel to the first façade, (2) an upper end and a lowerend, (3) a gap between the first façade and the second façade extendingfrom the lower end to the upper end, and (4) at least one mechanicalventilator (such as, but not limited to, a fan) positioned adjacent ornear the upper end of the DSF.

Before describing various embodiments of the present disclosure in moredetail by way of exemplary description, examples, and results, it is tobe understood that the embodiments of the present disclosure are notlimited in application to the details of methods and compositions as setforth in the following description. The embodiments of the presentdisclosure are capable of other embodiments or of being practiced orcarried out in various ways. As such, the language used herein isintended to be given the broadest possible scope and meaning; and theembodiments are meant to be exemplary, not exhaustive. Also, it is to beunderstood that the phraseology and terminology employed herein is forthe purpose of description and should not be regarded as limiting unlessotherwise indicated as so. Moreover, in the following detaileddescription, numerous specific details are set forth in order to providea more thorough understanding of the disclosure. However, it will beapparent to a person having ordinary skill in the art that the presentlydisclosed inventive concepts may be practiced without these specificdetails. In other instances, features which are well known to persons ofordinary skill in the art have not been described in detail to avoidunnecessary complication of the description.

Unless otherwise defined herein, scientific and technical terms used inconnection with the embodiments of the present disclosure shall have themeanings that are commonly understood by those having ordinary skill inthe art. Further, unless otherwise required by context, singular termsshall include pluralities and plural terms shall include the singular.

All patents, patent applications (including U.S. Provisional ApplicationSer. No. 62/814,643, filed Mar. 6, 2019), patent applicationpublications, and non-patent publications mentioned in the specificationare indicative of the level of skill of those skilled in the art towhich embodiments of the present disclosure pertain. All patents,published patent applications, and non-patent publications referenced inany portion of this application are herein expressly incorporated byreference in their entirety to the same extent as if each individualpatent or publication was specifically and individually indicated to beincorporated by reference.

While the apparatus and methods of the embodiments of the presentdisclosure have been described in terms of particular embodiments, itwill be apparent to those of skill in the art that variations may beapplied to the apparatus and/or methods and in the steps or in thesequence of steps of the method described herein without departing fromthe spirit and scope of the inventive concepts. All such similarsubstitutes and modifications apparent to those of skilled in the artare deemed to be within the spirit and scope of the inventive conceptsas defined herein.

As utilized in accordance with the apparatus and methods of theembodiments of the present disclosure, the following terms, unlessotherwise indicated, shall be understood to have the following meanings:

The use of the word “a” or “an” when used in conjunction with the term“comprising” in the claims and/or the specification may mean “one,” butit is also consistent with the meaning of “one or more,” “at least one,”and “one or more than one.” The use of the term “or” in the claims isused to mean “and/or” unless explicitly indicated to refer toalternatives only or when the alternatives are mutually exclusive,although the disclosure supports a definition that refers to onlyalternatives and “and/or.” The use of the term “at least one” will beunderstood to include one as well as any quantity more than one,including but not limited to, 2, 3, 4, 5, 6, 7, 8, 9, 10, 15, 20, 30,40, 50, 100, or any integer inclusive therein. The term “at least one”may extend up to 100 or 1000 or more, depending on the term to which itis attached; in addition, the quantities of 100/1000 are not to beconsidered limiting, as higher limits may also produce satisfactoryresults. In addition, the use of the term “at least one of X, Y, and Z”will be understood to include X alone, Y alone, and Z alone, as well asany combination of X, Y, and Z.

As used in this specification and claim(s), the words “comprising” (andany form of comprising, such as “comprise” and “comprises”), “having”(and any form of having, such as “have” and “has”), “including” (and anyform of including, such as “includes” and “include”), or “containing”(and any form of containing, such as “contains” and “contain”) areinclusive or open-ended and do not exclude additional, unrecitedelements or method steps.

The term “or combinations thereof” as used herein refers to allpermutations and combinations of the listed items preceding the term.For example, “A, B, C, or combinations thereof” is intended to includeat least one of: A, B, C, AB, AC, BC, or ABC, and if order is importantin a particular context, also BA, CA, CB, CBA, BCA, ACB, BAC, or CAB.Continuing with this example, expressly included are combinations thatcontain repeats of one or more item or term, such as BB, AAA, AAB, BBC,AAABCCCC, CBBAAA, CABABB, and so forth. The skilled artisan willunderstand that typically there is no limit on the number of items orterms in any combination, unless otherwise apparent from the context.

Throughout this application, the terms “about” or “approximately” areused to indicate that a value includes the inherent variation of error.Further, in this detailed description, each numerical value (such as,but not limited to, time or frequency) should be read once as modifiedby the term “about” (unless already expressly so modified), and thenread again as not so modified unless otherwise indicated in context. Theuse of the term “about” or “approximately” may mean a range including±1%, or ±5%, or ±10%, or ±15%, or ±25% of the subsequent number unlessotherwise stated.

As used herein, the term “substantially” means that the subsequentlydescribed event or circumstance completely occurs or that thesubsequently described event or circumstance occurs to a great extent ordegree. For example, the term “substantially” means that thesubsequently described event or circumstance occurs at least 90% of thetime, or at least 95% of the time, or at least 98% of the time.

As used herein any reference to “one embodiment” or “an embodiment”means that a particular element, feature, structure, or characteristicdescribed in connection with the embodiment is included in at least oneembodiment. The appearances of the phrase “in one embodiment” in variousplaces in the specification are not necessarily all referring to thesame embodiment.

Also, any range listed or described herein is intended to include,implicitly or explicitly, any number within the range, particularly allintegers, including the end points, and is to be considered as havingbeen so stated. For example, “a range from 1 to 10” is to be read asindicating each possible number, particularly integers, along thecontinuum between about 1 and about 10. Thus, even if specific datapoints within the range, or even no data points within the range, areexplicitly identified or specifically referred to, it is to beunderstood that any data points within the range are to be considered tohave been specified, and that the inventors possessed knowledge of theentire range and the points within the range. Thus, to illustrate,reference to a numerical range, such as 1-10 includes 1, 2, 3, 4, 5, 6,7, 8, 9, 10, as well as 1.1, 1.2, 1.3, 1.4, 1.5, etc., and so forth.Reference to a range of 1-50 therefore includes 1, 2, 3, 4, 5, 6, 7, 8,9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, etc., up to and including50, as well as 1.1, 1.2, 1.3, 1.4, 1.5, etc., 2.1, 2.2, 2.3, 2.4, 2.5,etc., and so forth. Reference to a series of ranges includes rangeswhich combine the values of the boundaries of different ranges withinthe series. Thus, to illustrate reference to a series of ranges, forexample, of 1-10, 10-20, 20-30, 30-40, 40-50, 50-60, 60-75, 75-100,100-150, 150-200, 200-250, 250-300, 300-400, 400-500, 500-750,750-1,000, includes ranges of 1-20, 10-50, 50-100, 100-500, and500-1,000, for example.

In certain embodiments, the aspect ratio of the urban street canyon,i.e., of canyon height to canyon width (average building height:averagestreet+sidewalk width, i.e., “H:W”) is in a range of about 0.5 to about2 or greater, such as, but not limited to, from about 0.5 to any ofabout 0.6, about 0.7, about 0.75, about 0.8, about 0.9, about 1.0, about1.1, about 1.2, about 1.3, about 1.4, about 1.5, about 1.6, about 1.7,about 1.8, about 1.9, about 2.0, about 2.5, about 3.0, about 4, about 5,about 6, about 7, about 8, about 9, about 10, or greater.

Returning now to the various non-limiting embodiments of the presentdisclosure, as shown herein, a modified double skin façade (DSF) isutilized on a building in an urban street canyon to influence flow andpollutant dispersion, thereby enhancing air quality in the urban streetcanyon. The modified DSF utilizes ventilation means (for example, butnot by way of limitation, fans or the HVAC system of the buildingitself) placed at various points within or near an open periphery of theDSF to increase the draw-through of air from a lower portion of the DSFto the open upper end of the DSF. The work described herein showed thatthe velocity profile for a building with a DSF can interact with streetlevel ventilation even without additional apparatus for providingventilation.

Numerical Analysis

The use of FLUENT is a recognized CFD software, universally acknowledgedfor energy, temperature, and flow analysis. Previous studies that showedthe interaction of building façades and in particular double-skinfaçades (DSF) with the streetscape were based upon the twin face type ofa DSF configuration that heavily relied upon natural convection, whereany fluid motion is caused by natural means such as the buoyancy effect.The buoyancy effect, similar to the chimney effect, is marked by warmerfluid rising and cooler fluid liquid falling. However, in the presentdisclosure, FLUENT was found to be incapable of allowing for theintroduction of a secondary air contaminant source. This did not allowthe FLUENT CFD software to be used to evaluate criteria pollutiontransport through the DSF.

It was identified that only flow analysis needed to be performed. Analternative CFD was identified, which utilized a very simplistic CFDapplication (Algorizk, Wind Tunnel). This CFD performs its simulationsby assuming an incompressible and homogeneous fluid and performinganalysis with Navier Stokes equations in a very simple 120×180 gridvelocity field. This simplistic structure allowed for CFD modeling thatincluded attributes that could combine urban canyon morphology, façadeintegrated DSF geometry, secondary flow sources, and wind speednecessary to identify mixing. This software did not, however, providematerial and fluid interactions nor scalable dimensional data. Hence,wind tunnel simulations were performed to validate results.

Wind Tunnel Analysis

Wind tunnel analysis is typically used in urban air pollutant dispersalstudies. It is important to note that urban boundary layer studies takeinto account Reynolds roughness factors. It has been found that there isReynolds-number independence of turbulent flow and pollutant dispersionin scaled building models. Reynolds-number independence can be expectedto model urban areas as long as the critical values of roughness andheight separation of the flow from the model were satisfied. It has beenshown that wind tunnel studies correspond well to results obtained inthe atmosphere by means of large eddy simulations so that they can beused with confidence for modelling urban situations. Typically, an urbanboundary layer wind tunnel simulation will also include a fetch ofroughness elements. The wind tunnel available for the present disclosurewas adapted to include elements that simulated urban boundary layerconditions.

Double Skin Façades—Evaluation and Selection

While the understanding of the capacity of the DSF to evacuate air atthe street level within the zone of influence is fundamental, thereremains the issue as to whether this could actually remove criteriapollutants from the streetscape where human interaction is beingpromoted.

Identifying the configuration of a DSF that is best suited forsupporting an integrated filtration system has been carried out in aprevious study (Abou-Nassar, Guy, Zahed Siddique, and Lee Fithian.“Computational Analysis to Design Energy Efficient Built Environments.”In ASME 2012 International Design Engineering Technical Conferences andComputers and Information in Engineering Conference, 177-186. AmericanSociety of Mechanical Engineers, 2012). The various definitions of DSFare characterized and described in the Belgian Building ResearchInstitute publication “Ventilated Double Skin Façades” (Loncour, X.,Deneyer, A., Blasco, M., Flamant, G., Wouters, P., “Ventilated DoubleSkin Façades, Classification & Illustration of Façade Concepts,”AIVC-CR03, 2005). The classification takes into account the modes of howthe façades work and introduces three criteria which are independent ofone another: 1) the type of ventilation (natural, mechanical, and hybridventilation); 2) the partitioning of the façade; and 3) the modes ofventilation of the cavity. The types of partitioning of the façade(shown and listed in FIG. 6 of U.S. Provisional Ser. No. 62/814,643)with pros and cons regarding their efficacy for interfacing with thestreet level and potential for providing natural ventilation aredescribed herein below.

Five ventilation technology types were identified (see FIG. 7 of U.S.Provisional Ser. No. 62/814,643) with the findings indicating only modes1 and 3 being able to address street level air zones.

There are numerous ventilations systems associated with DSF, and thisresearch isolated one for study due to how the airflow interacted at thestreetscape level. Two classification systems were identified, Britishand North American. In the British system, there are five primary typesbased on commonality of façade:

-   -   Category A: Sealed Inner Skin: subdivided into mechanically        ventilated cavity with controlled flue intake versus a        ventilated and serviced thermal flue;    -   Category B: Openable Inner and Outer Skins: subdivided into        single story cavity height versus full building cavity height;    -   Category C: Openable Inner Skin with mechanically ventilated        cavity with controlled flue intake;    -   Category D: Sealed Cavity, either zoned floor by floor or with a        full height cavity; and    -   Category E: Acoustic Barrier with either a massive exterior        envelope or a lightweight exterior envelope.

In the American system, there are three basic system types: BufferSystem, Extract Air System, and Twin Face System. The present disclosureincludes integrated biofilters to assist in the removal of criteria airpollutants.

Experimental Design and Analysis

Double skin façade airflow perpendicular to the urban canyon was modeledas this was the most extreme system exhibiting the least amount ofmixing. The model included windward and leeward applications of thesystem, to determine airflow ventilation. When decoupled from thebuilding environmental volumes and buoyancy effects, it was establishedthat mechanically assisted ventilation was necessary. All analysis wasconducted visually through video capture. The formation of a streetcanyon vortex was taken as an initial condition and subsequent removalof the tracer smoke source as evidence of evacuation.

CFD Analysis of the DSF and Urban Street Canyon

The data from the CFD software yielded preliminary results thatdetermined the technology was sufficient to producing mixing andevacuation at the streetscape level.

FIG. 2 illustrates the summary conditions of the relationship betweenthe urban canyon and the perpendicular airflow. Condition 1 illustratesa skimming flow regime that occurs over urban canyons and isdemonstrated by the visualization of the airflow and simple urban formswith streetscape in the CFD application. Condition 2 illustrates thesequestered condition that occurs in the urban canyon as the skimmingregime that creates the boundary layer and does not interact with thestreetscape air source. Condition 3 illustrates the introduction of aleeward side DSF with mechanical ventilation assist, demonstratingmixing of the boundary air and evacuation of the streetscape air source.Finally, Condition 4 illustrates the introduction of a windward side DSFwith mechanical ventilation assist, demonstrating mixing of the boundaryair and evacuation of the streetscape air source.

Wind Tunnel Analysis of the DSF and Urban Street Canyon

The experiments were performed in the OU AME Student Wind Tunnel (seeFIG. 11 of U.S. Provisional Ser. No. 62/814,643). The wind tunnel has atest section with dimensions 36″×36″×36″. In the wind tunnel, a scaledanalogue of the stratified boundary-layer flow was reproduced. Theboundary layer depth varied with each of the experiments. Maximum flowspeed in the tunnel was 3.76 m/s. For all studies, the height of thebuildings forming the canyon was 12 cm, and the length was 60 cm. Thedistance between the buildings was chosen to be 12 cm. This correspondsto the canyon aspect ratio equal to 1 and to the length-to-depth ratiosequal to 5 for a short canyon. In all experimental configurations, theexternal wind flow was directed perpendicular to the axis of the canyonseen as green laser axis, as shown in in FIGS. 3-7.

The boundary layer was generated at the entrance to the test section bytwo panels at the inlet and extending just to the test section. Thevertical profile was approximately 26 cm.

The investigated street canyon followed the experimental setup in“Wind-tunnel Study of Concentration Fields in Street Canyons”(Kastner-Klein, P, and E. J Plate. “Wind-Tunnel Study of ConcentrationFields in Street Canyons.” Atmospheric Environment 33, no. 24 (Oct. 1,1999): 3973-79). The geometric model scale calculated as the ratio ofthe model building height H=12 cm to typical average building heights inurban areas. Street width was 12 cm. The block length was 60 cm. Aceiling mounted collimated laser was used to maintain geometricalignment of the model and center the DSF within the test section. Thelaser also highlighted that portion of the air contaminant vortexturbulence for photographic capture.

Flow measurements in the tunnel were conducted using a hotwireanemometer. Turbulence characteristics were captured photographically todetermine whether the simulated DSF was interacting with air sourceswithin the canyon and evacuating. In parallel to the flow and turbulencecaptures, multiple types of passive tracer gases were used to simulatesequestered pollutants and buoyancy characteristics within the urbancanyon. Ambient temperature within the testing area was approximately90° F. (32° C.).

At a 1:200 scale, the DSF was simulated by a scaled opening (1.25 cm×4cm) in the middle of the block at the base of the “building” block andanother matching opening (1.25 cm×4 cm) at the top. The intent was tomimic a full-faced DSF across a typical building (lot size 50 feet)mid-block.

The typical DSF comprises a gap about 36″ wide. At 1:200 scale, thiswould have been too small to be effectively modeled; hence, the bottomand top openings were chosen to simulate the effect. Loss of fanefficiency due to the small openings necessitated the larger fan seen inthe middle of the model. The fan was coupled to a rheostat, and flowspeeds were measured with a hotwire anemometer. The inlet and outletspeeds of the simulated DSF are shown in Table 1. Differences in ¾ speedand full speed are minimal due to pressure loss between the blocks. Allstudies were conducted with DSF operating at full speed.

TABLE 1 Inlet and Outlet Speeds of the Wind Tunnel Inlet (m/s) Outlet(m/s) Quarter speed 3.1 0.81 Half speed 4.32 1.04 Three quarter speed5.03 1.53 MAX 5.03 1.30-1.53

Results and Discussion

Wind Tunnel Video Results

Test 1 utilized vaporized water and a glycol-based fluid. The vapormachine was placed to inundate the urban canyon to determine max timesfor evacuation. Wind Tunnel speed was set at 3.76 m/s. Flow speed of theDSF was set at MAX. Results are represented in FIG. 8.

Test 2 utilized dry ice vapor to simulate a trapped boundary layercondition. Hot smoke sources exhibited too much buoyancy even withambient temperatures of 90° F. The dry ice container was placed offsetto the DSF to show evacuation of pollutants generated at locationsfurthest from the DSF. Wind Tunnel speed was set at 3.76 m/s. Flow speedof the DSF was set at MAX. Results are shown in FIGS. 9-10.

Test 3 utilized a cold smoke generator to simulate a trapped boundarylayer condition. Hot smoke sources exhibited too much buoyancy even withambient temperatures of 90° F. The smoke source was offset to the DSF toshow evacuation of pollutants generated at locations furthest from theDSF. Wind Tunnel speed was set at 3.76 m/s. Flow speed of the DSF wasset at MAX. Results are shown in FIGS. 11-13.

In Test 4, due to extremely variable speeds within the wind tunnel,which affected the development of the boundary layer, an extreme testwas set up using a jet source to achieve higher speeds (10 m/s) at 23 cmabove the street level of the DSF. Dry ice vapor was used to simulate atrapped boundary layer condition. The dry ice container was placedoffset to the DSF to show evacuation of pollutants generated atlocations furthest from the DSF. A boundary layer jet funneled glycolvapor for visual identification of separation. Wind Tunnel speed was setat 0 m/s. Flow speed of the DSF was set at MAX. Results are shown inFIGS. 14-15.

Test 5 utilized a hot smoke tracer source similar to an HVAC ventilationtracer (wax impregnated cloth). The hot smoke source was placed insidethe DSF to demonstrate that the pollutants were not being removed fromthe streetscape merely by lift generated by the Bernoulli principle.Wind Tunnel speed was set at 3.76 m/s. Flow speed of the DSF was set atMAX. Results are shown in FIG. 16.

Discussion

Although many of the variables of the wind tunnel operation were lessthan ideal, what was consistent throughout all the tests was that theDSF evacuated the urban street canyon. Due to the nature of thesimulated pollutant sources, and the scale with which the DSF had tofunction (1:200), the pollutant sources were not able to be visuallytraced after entering the DSF inlet, as they were dissipated by the fanwithin the model.

In Test 1, a video named “Hot Smoke Works” was created of length 1:15.Vaporized water and glycol-based fluid was used with a 400 W fog machineto simulate the pollutant source. At time 0:04, the DSF Fan was turnedon, and at approximately 0:21, mixing was observed. Additional smoke wasgenerated due to the nature of the machine generating the smoke at 0:22,0:26, 0:28, and 0:42 time marks. FIG. 8 shows the canyon vortexbeginning to form at time mark 0:31, the vortex flow and movement towardthe DSF was visible at 0:34, and at 0:38, the vortex flow was stillvisible; however, it is apparent that the DSF was clearing the canyon.At 0:50, the canyon was cleared and skimming can be seen, and at the0:54 time mark, the model canyon was cleared and skimming continues.

In Test 2, a video named “Dry Ice Vapor Works” was created of length0:55. Dry Ice with a boundary layer was produced at 3.8 m/s. As shown inFIGS. 9-10, at the 0:05 time mark, the dry ice vapor can be seengathering in the model canyon; this is further shown at the 0:10 timemark. At the 0:15 time mark, the DSF was turned on, and dry ice vaporcan be seen entering the DSF, which is further shown at the 0:16 timemark. At the 0:21 time mark, the DSF was still on, and the dry ice vaporwas still seen entering the DSF. At the 0:38 mark, the DSF fan wasturned off, and as the fan slows, the dry ice vapor was seen filling themodel canyon again.

In Test 3, a video named “Cold Smoke Works” was created of length 0:29.A piece of equipment that burned wood chips and then cooled the smokewas used in the urban canyon model within the wind tunnel boundarylayer. As shown in FIGS. 11-13, at the 0:02 time mark, the cold smokewas seen entering the canyon. At the 0:05 time mark, the cold smoke canbe seen continuing to fill the model canyon, and at the 0:07 time mark,the smoke can be seen starting to develop the recirculation vortex. Atthe 0:09 time mark, the smoke was continuing to fill the model canyon,and recirculation of the vortex was readily apparent. The DSF fan wasturned on at the 0:12 time mark, and it can immediately be seen that therecirculation vortex was breaking up and entering the DSF. At time marks0:14 and 0:16, the recirculation continued to break up, entering the DSFand dissipating. At time mark 0:20, recirculation of the cold smoke wasalmost completely cleared, and the remaining smoke being generated wasbeing drawn toward the DSF. At time mark 0:27, recirculation of smokewas cleared, and the DSF was turned off.

In Test 4, a video named “Overall Viz” was created of length 0:50. DryIce with a simulated boundary layer jet of 10 m/s was used. This was dueto extremely variable speeds within the wind tunnel, which affected thedevelopment of the boundary layer. Dry Ice Vapor was used to simulatethe urban street canyon vortex condition. The boundary layer jetfunneled glycol vapor for visual identification of separation. As shownin FIGS. 14-15, at time mark 0:02, the dry ice vapor can be seengathering in the model canyon. At time mark 0:05, the boundary layer jetcan be seen. At time mark 0:16, the DSF was turned on, and the dry icevapor can be seen entering the DSF along with slight boundary layersmoke mixing. At time mark 0:21, the DSF fan remained on, and the dryice vapor can be seen entering the DSF along with more boundary layersmoke mixing. At time mark 0:28, the DSF fan remained on, and the dryice vapor was seen entering the DSF along with the model canyon beingcleared. At time mark 0:38, the DSF fan was turned off. At time mark0:40, the DSF fan was off, and dry ice vapor can be seen gathering inthe model canyon.

In Test 5, a video named “Inside Wall Works Only with Fan” was createdof length 0:32. For this video, a hot smoke tracer source was usedsimilar to the HVAC ventilation tracer smoke (wax impregnated cloth).The hot smoke source was placed inside the DSF to demonstrate that thepollutants were not being removed from the streetscape merely by liftgenerated by the Bernoulli principle. As shown in FIG. 16, at time mark0:02, the hot smoke was seen exiting the DSF wall at the inlet. At timemark 0:04, the DSF fan was turned on. At time mark 0:09, no smoke can beseen exiting the DSF wall at the inlet. At time mark 0:16, the DSF fanwas turned off. At time mark 0:23, smoke can again be seen exiting theDSF at the inlet.

In order to determine whether the flow rates of evacuation would bewithin the range suitable for an integrated biofilter to remediatepollutants, an off the shelf smoke evacuation fan was selected of a sizethat would fit within the DSF at full scale. Calculations show that theDSF results could be simulated with 14 fans mounted along the top of theDSF and within the face of a typical 50-foot building operating atspeeds of 3.76 m/s (Table 2).

TABLE 2 Ventilation Fan Specifications for a Non- Limiting Embodiment ofa Fan-Equipped¹ DSF Calculations for DSF Evacuation at MAX COMFORT 5 m/sand scaled requirements for fans Fan Dimensions 36″ blade diameter FanCFM 17886 Fan m³/s   8.44 ft² inlet area of DSF  258 m²   23.97 MAXCOMFORT m/s   5 (Fan m³/s*x/23.97) = 5 Number of Fans: x = (23.97*S)/Fanm³/s x = 119.85/Fan m³/s   14 Space required across face of building 36″fan size ft = (36/12)*# of fans   42.6 Experimental Results Scaled FanSpeed m/s   3.76 Max Speed of inlet for DSF simulation was 3.76 m/sInlet/Outlet size of DSF was 1 cm × 4 cm simulating 3 ft deep DSF acrossa 50 ft wide building width in canyon ¹Fan is a Canarm Ltd. Brand RBBelt Drive Propeller Upblast Roof Exhaust fan Industrial/Commercial Gen.Applic. CFM Range 6, 261-61,562. 36”, 3 Hp, TEFC, 208-230/460 V, 3Phase, 940 RPM, 17,866 CFM at 0” S.P.

The present disclosure demonstrated that the DSF, with or without themechanical ventilation assist, can interact with the streetscape levelair to improve and enhance mixing at the urban boundary layer and assistin the evacuation of criteria air pollutants from urban street canyons.This façade technology based approach yields the promise and expressionof a building DSF that serves a functional purpose beyond naturalventilation, daylighting, and thermal efficiency. This presents atransformative approach to building design, allowing the façade toenhance adjacent airspace and effectively creating a design interventionwith the building façade that can remove some of the criteria airpollutants found in these urban street canyon configurations.Optionally, the inclusion of a biofilter enables the further removal ofcriteria air pollutants such as VOCs and PMs in a manner thatsimultaneously satisfies the need for nature within the builtenvironment.

Although an illustrative implementation of one or more embodiments areprovided herein, the disclosed systems and/or methods may be implementedusing any number of techniques, whether currently known or in existence.The disclosure should in no way be limited to the illustrativeimplementations, drawings, and techniques illustrated herein, includingthe disclosed exemplary designs and implementations, but may be modifiedwithin the scope of the appended claims along with their full scope ofequivalents.

What is claimed is:
 1. A method of enhancing air quality in a streetcanyon, comprising: constructing a double skin façade (DSF) on abuilding, wherein the DSF comprises: a first façade; a second façadefacing and substantially parallel to the first façade; an upper end anda lower end; a gap between the first façade and the second façadeextending from the lower end to the upper end; and at least onemechanical ventilator positioned adjacent or near the upper end of theDSF; and causing the at least one mechanical ventilator to be in anoperational mode, whereby movement of air is driven in an upwarddirection toward the upper end of the DSF causing movement of aircontaminants from the lower end of the DSF to the upper end of the DSF,thereby enhancing the air quality of the street canyon by removing aircontaminants from a street level adjacent the building.
 2. The method ofclaim 1, wherein the at least one mechanical ventilator is a fan.
 3. Themethod of claim 1, wherein the street canyon has an aspect ratio of atleast about 1.0.
 4. The method of claim 1, wherein the street canyon hasan aspect ratio of at least about 1.5.
 5. A building having a capabilityof enhancing quality of the air adjacent the building, the buildingcomprising: a double skin façade (DSF), wherein the DSF comprises: afirst façade; a second façade facing and substantially parallel to thefirst façade; an upper end and a lower end; a gap between the firstfaçade and the second façade extending from the lower end to the upperend; and at least one mechanical ventilator positioned adjacent or nearthe upper end of the DSF; and wherein when the at least one mechanicalventilator is in an operating mode, the at least one mechanicalventilator drives movement of air in an upward direction toward theupper end of the DSF causing movement of air contaminants from the lowerend of the DSF to the upper end of the DSF, thereby enhancing the airquality adjacent the building by removal of the air contaminants from astreet level adjacent the building.
 6. The building of claim 5, whereinthe at least one mechanical ventilator is a fan.
 7. The building ofclaim 5, wherein the street canyon has an aspect ratio of at least about1.0.
 8. The building of claim 5, wherein the street canyon has an aspectratio of at least about 1.5.